John Iliffe <john.iliffe@iliffe.ca> writes:
> Can anybody tell what these files are and what they do, and more importantly
> if they are needed?
They are database table files, and you will certainly be unhappy if you
just manually rm them.
You can read some theory here:
https://www.postgresql.org/docs/9.2/static/storage.html
and for help in identifying specific files you might like oid2name:
https://www.postgresql.org/docs/9.2/static/oid2name.html
although it's certainly possible to get the same results with manual
queries on the system catalogs.
regards, tom lane
